1. Field of the Invention
The present invention relates to a rewritable optical recording medium, and a method for formatting the same.
2. Background of the Invention
In general, optical recording media may be classified into a ROM type for read only, a WORM type for writing once, and a rewritable type for repetitive writing. In rewritable optical recording media, i.e., optical disks, which are rewritable freely and repetitively, there are CD-RW (Rewritable Compact Disc), and rewritable digital versatile discs (DVD-RAM, DVD-RW). In those rewritable optical disks, information writing/reading thereto/therefrom is repetitively performed due to the nature of use of the optical disk. The repetitive writing and reading of information causes a mixing ratio of a recording layer mixture, provided for recording the information, to change from an initial mixing ratio. This change leads to a loss of initial properties of the mixture, which causes errors during writing/reading information, termed degradation. Areas of degradation are turned up as defective areas when formatting, reading, or writing to the optical disk is carried out.
Other than such degradation, defective areas of the rewritable optical disk are caused by scratches on a surface, dust, and/or production defects. Therefore, in order to prevent writing/reading data to/from the defective areas by the foregoing, management of the defective areas is required. To do this, as shown in FIG. 1, DMAs (Defect Management Areas) are provided in a lead-in area and in a lead-out area of the optical recording medium for managing the defective areas of the optical recording medium. Also, data areas are managed in zones (or groups), each zone having a user area for use in actual writing of data and a spare area for use in a case of defect occurrence in the user area. In general, there are four DMAs provided in one disk (for example, a DVD-RAM)xe2x80x94two in the lead-in area and two in the lead-out area. As management of the DMAs are important, the same data is repeatedly written in the four DMAs for protection of data. Each DMA has two blocks having 32 sectors in total, i.e., one block has 16 sectors. Each DMA has a PDL (Primary Defect List) which is a primary data storage and an SDL (Secondary Defect List) which is a secondary data storage.
In general, the PDL stores entries of defects that occurred during fabrication of the disk, as well as all defective sectors identified in initializing (and re-initializing) of the disk. Each entry in the PDL has an entry type and a sector number of a defective sector. The SDL, listed in block units, stores entries of defective areas that occurred after initializing, or defective areas which can not be listed on the PDL during initializing. Each SDL entry has an area for storing a sector number of a first sector of a defective block having a defective sector therein. Each SDL entry also has an area for storing a sector number of a first sector of a replacement block for replacing the block containing the defective sector. The defective areas (i.e., defective sectors or defective blocks) in the data area are replaced by good areas, according to a slipping replacement algorithm or linear replacement algorithm.
Referring to FIG. 2A, in the slipping replacement when a defective area is listed on the PDL, if the defective sector is present in the user area on which data is to be written, the defective sector is skipped. The defective sector is replaced with a good sector next to the defective sector when writing the data. The user area in which the data is being written is pushed backward to occupy the spare area by as many sectors as the skipped defective sectors. That is, as much spare area is assigned to the user area as corresponds to the skipped sectors. For example, if there are two defective sectors listed on the PDL, the user area in which the data will be written is pushed backward up to two sectors of the spare area.
Referring to FIG. 2B, in the linear replacement when a defective area is listed on the SDL, if a defective block listed on the SDL is present in the user area, the defective block is replaced with a corresponding block in the spare area when writing the data.
Besides the method of assigning the spare area as shown in FIG. 1, there are other methods for assigning the spare area either to any one zone of the data area, or a portion of the data area. Of the methods for assigning the spare area to one portion of the data area, there are methods for assigning the spare area to a top, i.e., only to an inner circumference of the data area in the initial formatting as shown in FIG. 3A, to a bottom, i.e., only to an outer circumference as shown in FIG. 3B, or to an inner and an outer circumferences as shown in FIG. 3C. For convenience of explanation, the spare area assigned to the inner circumference is called an inner circumference spare area, and the spare area assigned to the outer circumference is called an outer circumference spare area. The user area is the remaining data area after the inner spare area, the outer spare area, or the inner and the outer spare areas are excluded. In this instance, no LSN (Logical Sector Number) is given to the spare area assigned in a process of initial formatting. When only the inner spare area or the outer spare area is assigned during initial formatting, if the spare area assigned becomes full, another spare area may be assigned to an opposite side as necessary. In such case, both the inner spare area and the outer spare area are present as shown in FIG. 3C.
Provided defective sectors are listed on the PDL during initializing or re-initializing, a recording capacity is correspondingly reduced, since no data is written on the defective sectors. The user area slips into the spare area as many sectors as the defective sectors listed on the PDL to maintain an initial data recording capacity. That is, there is a change in the user area. However, there is no definition of how to make the slipping replacement in the spare area when the spare area is assigned both to the inner circumference and the outer circumference of the data area. If the slipping is conducted in a reverse order in the outer circumference spare area, the data being written is separated, i.e., becomes discontinuous, as shown in FIG. 4. The outer spare area is assigned to the user area in a reverse order, which makes realtime continuous data writing difficult. As shown in FIG. 1, when the spare area is assigned in zones, realtime continuous data writing is difficult, because the spare area is present between zones. Discontinuity of the user area, whatever the cause, is an obstacle to the realtime writing.
Accordingly, the present invention is directed to an optical recording medium and a method for formatting the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide an optical recording medium which can always maintain continuity of a user area regardless of initializing.
Another object of the present invention is to provide a method for formatting an optical recording medium, in which slipping is conducted in a direction such that continuity of a user area is maintained during initializing.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, a method for formatting an optical recording medium, the optical recording medium having a user area and a spare area, includes subjecting the spare area to slipping replacement in a reverse order if the spare area is located at an inner circumference of the user area; and subjecting the spare area to slipping replacement in a forward order if the spare area is located at an outer circumference of the user area.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.